Mechanism of alkyne alkoxycarbonylation at a Pd catalyst with P,N hemilabile ligands: a density functional study.
Chemistry
; 20(43): 13923-6, 2014 Oct 20.
Article
em En
| MEDLINE
| ID: mdl-25195574
ABSTRACT
A detailed mechanism for alkyne alkoxycarbonylation mediated by a palladium catalyst has been characterised at the B3PW91-D3/PCM level of density functional theory (including bulk solvation and dispersion corrections). This transformation, investigated via the methoxycarbonylation of propyne, involves a uniquely dual role for the P,N hemilabile ligand acting co-catalytically as both an in situ base and proton relay coupled with a Pd(0) centre, allowing for surmountable barriers (highest ΔG(≠) of 22.9â
kcal mol(-1) for alcoholysis). This proton-shuffle between methanol and coordinated propyne accounts for experimental requirements (high acid concentration) and reproduces observed regioselectivities as a function of ligand structure. A simple ligand modification is proposed, which is predicted to improve catalytic turnover by three orders of magnitude.
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MEDLINE
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En
Ano de publicação:
2014
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Article